Fuel cells have been used as a power source in many applications. For example, fuel cells have been proposed for use in electrical vehicular power plants to replace internal combustion engines. In proton exchange membrane (PEM)-type fuel cells, hydrogen is supplied to the anode of the fuel cell and oxygen is supplied as the oxidant to the cathode. PEM fuel cells include a membrane electrode assembly (MEA) comprising a thin, proton transmissive, non-electrically conductive solid polymer electrolyte membrane having the anode catalyst on one of its faces and the cathode catalyst on the opposite face. The MEA is sandwiched between a pair of electrically conductive elements, sometimes referred to as the gas diffusion media components, that: (1) serve as current collectors for the anode and cathode; (2) contain appropriate openings therein for distributing the fuel cell's gaseous reactants over the surfaces of the respective anode and cathode catalysts; (3) remove product water vapor or liquid water from electrode to flow field channels; (4) are thermally conductive for heat rejection; and (5) have mechanical strength. The term fuel cell is typically used to refer to either a single cell or a plurality of cells (e.g., a stack) depending on the context. A plurality of individual cells are commonly bundled together to form a fuel cell stack and are commonly arranged in series. Each cell within the stack comprises the MEA described earlier, and each such MEA provides its increment of voltage.
In PEM fuel cells, hydrogen (H2) is the anode reactant (i.e., fuel) and oxygen is the cathode reactant (i.e., oxidant). The oxygen can be either a pure form (O2), or air (a mixture of O2 and N2). The solid polymer electrolytes are typically made from ion exchange resins such as perfluoronated sulfonic acid. The anode/cathode typically comprises finely divided catalytic particles, which are often supported on carbon particles, and mixed with a proton conductive resin. The catalytic particles are typically costly precious metal particles. These membrane electrode assemblies are relatively expensive to manufacture and require certain conditions, including proper water management and humidification, and control of catalyst fouling constituents such as carbon monoxide (CO), for effective operation.
Examples of technology related to PEM and other related types of fuel cell systems can be found with reference to commonly-assigned U.S. Pat. Nos. 3,985,578 to Witherspoon et al.; 5,272,017 to Swathirajan et al.; 5,624,769 to Li et al.; 5,776,624 to Neutzler; 6,103,409 to DiPierno Bosco et al.; 6,277,513 to Swathirajan et al.; 6,350,539 to Woods, III et al.; 6,372,376 to Fronk et al.; 6,376,111 to Mathias et al.; 6,521,381 to Vyas et al.; 6,524,736 to Sompalli et al.; 6,528,191 to Senner; 6,566,004 to Fly et al.; 6,630,260 to Forte et al.; 6,663,994 to Fly et al.; 6,740,433 to Senner; 6,777,120 to Nelson et al.; 6,793,544 to Brady et al.; 6,794,068 to Rapaport et al.; 6,811,918 to Blunk et al.; 6,824,909 to Mathias et al.; U.S. Patent Application Publication Nos. 2004/0229087 to Senner et al.; 2005/0026012 to O'Hara; 2005/0026018 to O'Hara et al.; and 2005/0026523 to O'Hara et al., the entire specifications of all of which are expressly incorporated herein by reference.
For automotive applications, PEM fuel cells must be operable down to −40° C. Silicone, or fluorosilicone, gaskets can provide adequate sealing for fuel cells down to this temperature, but are believed to leach out undesirable contaminants and fillers in the fuel cell internal operating environment, e.g., through the internal wetted surface. These contaminants are believed to poison the catalysts and proton-conduction sites of the membranes, and degrade the gasket. Other gasket materials, such as EPDM, have been resistant to the harsh internal environment of the PEM fuel cell, and do not contaminate the membrane or degrade the sealing qualities. One significant drawback, however, is that EPDM, with its higher glass transition temperature, has been shown to not seal as well, especially at relatively cold temperatures.
Accordingly, there exists a need for a new and improved fuel cell gasket that has enhanced low temperature sealing and membrane contamination resistance characteristics.